… But we in the language lab use the (dual function microphone/line-in) "rear input" for our headsets (for ergonomic, health&safety and security reasons). Workaround here.

Apparently this startup behavior cannot be changed within Saba Centra:

Any startup will bring up the “Audio Wizard” asking users, even in a controlled lab environment, to configure their audio devices,

and if users do (and choose what they have: headset), make wrong assumptions which audio plug to enable (“Microphone” front panel, even if your headset is plugged into the rear panel dual “line-in/microphone”)